Laboratory for underground nuclear astrophysics (LUNA): First results of the measurements of the reaction [sup 3]He([sup 3]He,2p)[sup 4]He at solar energies

Abstract

A compact 50 kV accelerator facility has been installed in the underground laboratory of the Laboratori Nazionali del Gran Sasso (LNGS) in Italy in the framework of the LUNA—project. Because of the specially designed accelerator setup and the suppression of the cosmic ray background in the underground laboratory the sensitivity of the set up gives the possibility to measure the cross sections of nuclear reactions at energies far below the coulomb barrier, where cross sections are as low as a few fbarn. Currently the reaction 3He(3He,2p)4He, which is important for the Solar Neutrino Puzzle, is being investigated at energies relevant in our sun (E=15–27 keV). These are the first direct measurements of a nuclear cross section covering the whole thermal energy range of the solar plasma. This contribution reports on the measurements covering the energy range between E=20.7 keV and 25 keV.